Foundry composition



United States Patent 1 Patented Oct. 20, 1970 hoe 3,535,131 FOUNDRY COMPOSITION Vernon C. Meier, 3215 Jackson Ave., Davenport, Iowa 52802 No Drawing. Continuation-impart of applications Ser. No.

595,264, Nov. 17, 1966, Ser. No. 737,858, June 18,

1968, and Ser. No. 807,924, Mar. 17, 1969. This application Nov. 20, 1969, Ser. No. 878,585

Int. Cl. B28b 7/34 US. Cl. 106-38.35 12 Claims ABSTRACT OF THE DISCLOSURE An improved green sand composition for foundry purposes is provided by adding a compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate, and a small amount of a pregelatinized starch to the conventional green sand composition in an amount sufiicient to prevent gassing.

This patent application is a continuation-in-part of applicants previously filed patent application Ser. No. 595,264, filed Nov. 17, 1966, now abandoned, applicants previously filed patent application Ser. No. 737,858, filed June 18, 1968, now abandoned, and applicants previously filed continuation-in-part application Ser. No. 807,924, filed Mar. 17, 1969, now abandoned.

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon,

The present invention relates to a foundry composition and more particularly to an improved foundry sand, the composition of which is particularly beneficial in the preparation of green sand molds and green sand cores whereby a substantially gas-free core or mold is provided.

Background of the invention Foundries have constantly strived for high quality molded products through improved green sand compositions in an effort to eliminate core gas, core sag, difficult shake out, hot tearing, veining, sand contamination, and other objectionable characteristics incident to standard or conventional foundry practices. It is well-known that green sand mold compositions possess the characteristic that fissures and cracks are created in the surface of the mold incident to wash of the molten metal and which allows the molten metal to enter therein and produce veins or fins, scabs, or rattails. The molten metal which penetrates the mold also causes gas to form which causes expansion and helps promote hot tears. Efforts to eliminate such problems have been partially succesful through the use of surface coatings which are sprayed or otherwise applied to the mold after it is formed and prior to use for casting. 'But such practices are of limited success since they affect only the surface pores or cracks. The mold still possesses the tendency to crack and cause fissures and the advantage gained by surface coatings is to provide a smoother surface. Although such practices are found advantageous, they do not liminate entirely the problems incident to green sand mold compositions.

Accordingly, it is a primary object of the present invention to provide an improved composition of matter for foundry purposes which will effect greater efficiency and perfection in the manufacture of metal castings.

It is another object of the present invention to provide an improved foundry composition which will reduce the number of defective finished product metal castings.

Still another object of the present invention is to reduce contamination in the green sand composition thereby to effect good detail and finish in the metal casting as well as lower sand costs.

Also, it is an object of the present invention to eliminate hot tears through reducing the formation of gasses in the mold or core and reducing sand expansion as well as inducing better mold or core collapsibility.

It is a further object of the present invention to provide an improved composition for green sand 'molds and cores which is substantially gas-free, eliminates veining, and produces a smooth surface continuity for the finished metal casting.

Another object of the present invention is to provide an improved foundry sand composition which displays extremely high green strength, eliminates hot tears through reducing the formation of gasses, eliminates veining, and produces a better finished product at a lower cost by eliminating expensive machining operations and reduction of defective castings.

Summary of the invention In accordance with the present invention, an improved green sand foundry composition is provided by admixing with the binder of such composition a quantity of a compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate in an amount sufiicient to prevent gassing, and, if desired, a small quantity of pregelatinized starch in an amount sufficient to increase the tensile strength of the composition thereby to facilitate handling.

Description of the preferred embodiments The novel features characteristic of the present invention, as well as additional objects and advantages thereof, will be understood better from the following detailed description, illustrated by way of preferred examples of a foundry composition in accordance with the present invention. The following preferred compositions are given by way of illustration which should not be taken as limiting the present invention to the specific parts by weight.

EXAMPLE I Percentage by weight, about Silica sand 89.3 Bentonite 4.0 Corn flour 0.4 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 3.4 Alumina silicate 0.4 Water 2.5

EXAMPLE 2 Percentage by weight, about Silica sand 9 1.1 Bentonite 3.3 Corn flour 0.5 Compound selected from the group consisting if titanium silicate, zirconium silicate, and hafnium silicate 2.7 Water 2.4

EXAMPLE 3 Percentage by weight, about Silica sand 1 87.6 Bentonite 47 Corn flour 0.4 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 3.9 Alumina silicate 0.9 Water 2.5

3 EXAMPLE 4 Percentage by weight, about Silica sand 89.3 Binder mixture of bentonite and corn flour 4.4 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 3.4 Alumina silicate 0.4

Water 2.5

EXAMPLE 5 Percentage by weight, about Silica sand 89.3

Bentonite 4.0 Corn flour 0.4 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 3.8 Water 2.5

EXAMPLE 6 Percentage by weight, about Silica sand 91.06

Bentonite 1.52 Corn fiour 0.30 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 4.53

Pregelatinized starch 0.06 Water 2.53

EXAMPLE 7 Percentage by weight, about Silica sand 91.11

Bentonite 0.611 Corn flour 0.46 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 4.55

Pregelatinized starch 0.08 Water 3.19

EXAMPLE 8 Percentage by weight, about Silica sand 89.3 Bentonite 4.0 Corn flour 0.4 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 3.65 Pregelatinized starch 0.15 Water 2.5

The above-described formulas have demonstrated that they are ideally suited for making molds and cores which are substantially gas free, require a minimum setting time, and produce a remarkable product having good detail and finish with a minimum of cleaning. It will be recognized by persons skilled in the art that the ingredients comprising the binder portion of the above-identified compositions may be prepared and packaged in suitable fashion for convenience of transportation, later to be combined with silica sand and water at locations where the compositiin will be used. In such event, the preferred binder compositions will be found to comprise in themselves the following:

EXAMPLE 9 Percentage by weight, about Bentonite 48.7

Corn flour 5.4

Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 40.5

Alumina silicate 5.4

4 EXAMPLE 10 Percentage by weight, about Bentonite 50.7

Corn flour 7.7 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 41.5

EXAMPLE 11 Percentage by weight, about Bentonite 47.4

Corn flour 4.0

Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 39.4

Alumina silicate 9.1

EXAMPLE 12 Percentage by weight, about Binder mixture of bentonite and corn flour 53.6

Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 41.5

Alumina silicate 4.8

EXAMPLE 13 Percentage by weight, about Bentonite 51.43

Corn flour 5.71 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 42.85

EXAMPLE 14 Percent by weight, about Bentonite 23.69 Corn flour 4.74 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 70.68

Starch 0.89

EXAMPLE 15 Percent by weight, about Bentonite 10.6

Corn flour 8.0 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 80.0 Pregelatinized starch 1.4

Although the specific proportions of ingredients above described have been given as preferred embodiments, it is possible to make the foundry composition of the present invention without adhering to the stated proportions. Depending upon the particular application, and other foundry considerations, the foundry composition of the present invention is susceptible of variation within the following ranges:

Percentage by weight, about Silica sand -95 Binder 20-5 If, as stated above, it is desired to mix the binder portion of the above-identified compositions for transportation, the binder itself will be found susceptible of variation within the following ranges:

Percentage by weight, about Bentonite 10.6 to 51.43

Corn flour 4.0 to 8.0 Compound selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate 39.4 to 80.0 Alumina silicate 0.0 to 9.1 Pregelatinized starch 0.0 to 1.8

Although the above components may be varied within the ranges indicated, for best results, a certain degree of care should be exercised in selection of the components. For example, a silica sand is preferred having an A.F.S. range of 55 to 90. Likewise, a western type bentonite is preferred over other types. The quantity of corn flour should be kept to a minimum since it has the characteristic of generating gas. With respect to the silicate compound, the compound selected by preference from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate is zirconium silicate since it is readily obtainable as compared to the others. Nevertheless, either one of the other two silicates may be substituted for the zirconium silicate with equivalent results. However, the quantity of compound should be controlled because too little compound has the tendency to lose bond and too much compound makes the composition too sticky or gummy.

The present invention is susceptible of practice with or without the use of a pregelatinized starch, as will be noted by the above-identified preferred examples. Although elimination of gas is a consequence of the use of the silicate compound, excellent results are achieved without the use of the starch. However, the use of such a starch is preferred since it tends to increase the tensile strength of the mold or core thereby facilitating handling. Effective amounts of pregelatinized starch for this purpose may range up to 0.15 percent by weight of the entire foundry composition or up to about 1.8 percent by weight of said binder, if the binder is premixed separately. In addition, since the quantity of starch is relatively small, close control should be particularly emphasized in view of the fact that excessive starch creates a sticky non-flowing sand and results in a core having high tensile strength and hard core surfaces. On the other hand, too little starch gives a core of relatively low tensile strength and soft core surfaces. The preferred type of starch is an instant granular starch which reacts very quickly with water. The type of starch which has produced the best results is that referred to herein as a pregelatinized starch which is readily obtainable on the market under the trade name Niagara Instant Starch. The Niagara Instant Starch is a product of Corn Products Refining Company. This companys starch is described in detail in U.S. Pat. 2,609,326 issued Sept. 2, 1952 to W. W. Pigman, et al., for Cold Water Dispersible Starch Product and Method of Preparing the Same. Although other starches of like kind may be used, experience has shown that the Niagara Instant Starch is preferred over the others.

It will also be recognized by persons skilled in the art that silica flour may be introduced into the above-identified compositions for the purpose of controlling the permeability of the sand. The quantity of silica flour used may vary between 1 to 4 parts by weight of the entire composition and depends upon the particular sand grain size since its function is to densify the sand. Accordingly, the finer the sand grain size, the less silica flour is required. Similarly, the addition of a small percentage of alumina silicate to compositions not utilizing the starch is a matter of choice but it will be found to be 'a substitute in lieu of starch from the standpoint that it facilitates handling of the mold or core since it increases the hardness or tensile strength of the mold or core.

In carrying out the composition of the present invention, excellent results have been achieved from the above formulations by intimately mixing the ingredients employing the following method. The silica sand is intermixed with the binder by addition to the sand the hentonite, corn flour, and starch. If silica flour is used, this should be added at the same time. The mixture is mulled dry for several minutes or sufliciently to thoroughly mix the ingredients. Mulling iswontinued while three quarts of water are slowly added thereto. This mixture is then mulled for about 3 minutes. The zirconium silicate is then added while mulling continues and the entire contents are mulled for about 5 minutes. Up to approximately one more quart of water, in an amount sufiicient to plasticize the mixture, is then added slowly until the moisture content (2. to 3.2 percent of the mass) is suitable for compounding the ingredients into the finished or final form. A composition prepared in this manner will require a minimum drying time, normally only long enough to eliminate approximately 3 percent moisture.

If, however, it is desired to prepare the binder itself for shipment to locations where it will then be combined with silica sand and water, it will be found expedient to prepare the zirconium silicate in a paste form and ship it separately from a dry mixture of bentonite, corn flour, and starch in appropriate quantities. On location, the binder ingredients may then be added to the sand and the admixing continued as above outlined.

By following the practices outlined herein, the improved green sand composition will be found ideally suited for making molds and cores which are substantially, if not entirely gas-free, and which will allow the metal to fiow over the mold or core without the necessity of sealing or venting. Molds and cores will be found to possess excellent strength characteristics and yet be conducive to desirable shake out. Venting or mudding of seams is eliminated since sag encountered with baked sand is lacking. Not only will castings require a minimum of cleaning, but also the sand is free of contamination and can be mixed and used repeatedly.

It will be recognized by persons skilled in the art that the improved foundry composition of the present invention will result in many advantages in addition to those outlined herein. Therefore, it will be appreciated that certain changes and variations may be made in the specific formulations set forth herein without departing from the scope of the present invention. Accordingly, it is to be understood that the novelty and scope of the present invention is not intended to be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims.

I claim:

1. In a composition of matter for foundry purposes containing a major proportion of silica sand and a binder comprising bentonite and corn flour in effective amounts sufiicient to bind said sand: the improvement comprising as an additive in said binder, a silicate selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate in an effective amount sufiicient to prevent gassing.

2. The invention according to claim 1, wherein said binder comprises about 5 to about 20 percent by weight of said composition of matter.

3. The invention according to claim 1, wherein said silicate comprises about 39.4 percent to about 80.0 percent by weight and of said binder.

4. The invention according to claim 1, wherein said silicate is zirconium silicate.

5. The invention according to claim 1, wherein said binder also includes pregelatinized starch in an effective amount sufficient to increase the tensile strength of said composition of matter.

6. The invention according to claim 5, wherein said pregelatinized starch is in an elfective amount of up to about 0.15 percent by weight of said composition of matter.

7. In a binder for a green sand composition having a major proportion of silica sand; said binder containing bentonite and corn flour: the improvement comprising, as an additive in said binder, a silicate selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate, in an effective amount sufficient to prevent gassing in said green sand composition.

8. The invention according to claim 7, wherein said silicate comprises about 39.4 percent to about 80.0 percent by weight of said binder.

9. The invention according to claim 7, wherein there is also added to said binder a pregelatinized starch in an efi'ective amount up to about 1.8 percent by weight of said binder.

10. The invention according to claim 8, wherein said silicate is zirconium silicate.

11. In a binder for a green sand composition having a major proportion of silica sand, said binder containing about 10.6 to about 51.43 percent by Weight of bentonite and about 4.0 to about 8.0 percent by weight of corn flour: the improvement comprising, as an additive in of a silicate selected from the group consisting of titanium silicate, zirconium silicate, and hafnium silicate.

12. The invention according to claim 11, wherein said silicate is zirconium silicate.

References Cited UNITED STATES PATENTS 4/1950 Kerlin. 2/1958 Dietert et a1.

JULIUS FROME, Primary Examiner L. B. HAYES, Assistant Examiner US. Cl. X.R.

said binder, about 39.4 to about 80.0 percent by weight 15 106 38 5, 57, 71 

